I think this is more an issue of logistics getting absurd wp bonuses then needing a cap. If WP rewards for logis were curtailed to be more like dropship points and equipment destruction, things would be better. One guy reloading his gun once on a nanohive shouldn't give twice as much WP as said nanohive being destroyed.

If:
Triage: 10
Guardian: 5
Spawn link: 10
Resupply: 5

Logis wouldn't have such broken WP gain.

You might say what do you care? I care because I don't want to be taking objectives and killing redberries only to lose 50k-100k isk on my pay out because some logi on my team equipment spammed to get a huge piece of the isk pie on our team. Payouts are based on the teamplayers contribution to the team as a whole, which the game bases on WPs only. Those newberries dying and spawning to die again on your uplinks while pew pew eating armor and ammo resupplies isn't helping the team.

I know logis will probably go "Well see if we logi you!" Having half your team logi when they have no killing power is pretty much a quick way to lose and I would show logis to the door next to the snipers if they won't logi without broken WP gains. Logi slayers don't count, but logi slayers usually aren't all that good on the logi part.

We don't need a lot of logis or snipers, that's why I am an advocate of multiple role capability over specialize in one thing until you have 15 mil into it build which is suggested by everyone under the sun because its easier for vets to deal with players who are cookie cutter builds. This is why blueberries are considered "useless", because you only need so many auxiliary roles which tend to be in abundance on the field when people can't swap roles.